   ; In order to be correct, the voke collision system needs to maintain this invariant:
   ; at all times, no two entities are occuping the same space.
   ; By updating the JS-land collision system multiple times per tick, we maintain this invariant.
-  ; if we did not do this, two entities moving toward each other could both end up occuping
+  ; If we did not do this, two entities moving toward each other could both end up occuping
   ; the same space.
   (-update-entity-center (entity :id) new-center)
 


(sm/defn get-updated-entity-center :- Entity
  "Returns the given entity, with its most up-to-date center value spliced in.
  See `apply-movement`."
  [entity :- Entity]
  (assoc-in entity
            [:shape :center]

  [entity :- Entity
   new-center :- Vector2
   new-velocity :- Vector2]
  ; Queue an update to this entity's center and velocity; these updates get run in a single batch at the
  ; end of this tick, so that all entities in cljs-land have their centers+velocities updated at once.
  (update-entity! (entity :id)
                  :collision-system
                  (fn [entity]
